The overall objective of the work is to further our understanding of the neural control of posture and locomotion. We are studying the properties and central connections of muscle stretch receptors and joint afferents, the response of motoneurons and interneurons to proprioceptive inputs that simulate those occurring during natural movements and the neuronal substrate for the control of locomotion. The long-term goal of the proposed research is to contribute to our knowledge of the supraspinal control of posture and locomotion in both normal and abnormal states. It should be emphasized, however, that a great deal is yet to be learned concerning the spinal contribution to motor control particularly when the complexity of natural motion is added. It is hoped that these studies will contribute information basic to our understanding of the nervous control of both normal postural and locomotor activity and abnormal motor activity related to neurological disorders such as Parkinsonism, cerebellar diseases and spinal cord diseases including spinal cord injury.